U.S. patent number 8,431,515 [Application Number 12/601,992] was granted by the patent office on 2013-04-30 for tape-shaped oxide superconductor.
This patent grant is currently assigned to International Superconductivity Technology Center, The Juridical Foundation, N/A, SWCC Showa Cable Systems Co., Ltd.. The grantee listed for this patent is Yuji Aoki, Takayo Hasegawa, Atsushi Kaneko, Tsutomu Koizumi, Yasuo Takahashi. Invention is credited to Yuji Aoki, Takayo Hasegawa, Atsushi Kaneko, Tsutomu Koizumi, Yasuo Takahashi.
United States Patent |
8,431,515 |
Takahashi , et al. |
April 30, 2013 |
Tape-shaped oxide superconductor
Abstract
A tape-shaped oxide superconductor includes a 15 to 100 nm-thick
Ce--Gd--O-based oxide layer (Ce:Gd=40:60 to 70:30 molar ratio) and
a 100 nm-thick Ce--Zr--O-based oxide layer (Ce:Zr=50:50 molar
ratio) as first and second intermediate layers are formed by MOD on
an Ni-base alloy substrate having a half value width
(FWHM:.DELTA..phi.) of 6.5 degrees. A 150 nm-thick CeO.sub.2 oxide
layer as a third intermediate layer is formed on the second
intermediate layer by RF sputtering. A 1 .mu.m-thick YBCO
superconducting layer is formed by TFA-MOD on the three-layer
structure. In the tape-shaped oxide superconductor, the
.DELTA..phi. values of the first to third intermediate layers are
(6.0 to 6.5) degrees, (6.0 to 6.6) degrees, and (6.0 to 6.6)
degrees, respectively, and the Jc value of the YBCO superconducting
layer in liquid nitrogen is 1.8 to 2.2 MA/cm.sup.2.
Inventors: |
Takahashi; Yasuo (Tokyo,
JP), Koizumi; Tsutomu (Tokyo, JP), Aoki;
Yuji (Tokyo, JP), Kaneko; Atsushi (Tokyo,
JP), Hasegawa; Takayo (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Takahashi; Yasuo
Koizumi; Tsutomu
Aoki; Yuji
Kaneko; Atsushi
Hasegawa; Takayo |
Tokyo
Tokyo
Tokyo
Tokyo
Tokyo |
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP |
|
|
Assignee: |
International Superconductivity
Technology Center, The Juridical Foundation (JP)
N/A (JP)
SWCC Showa Cable Systems Co., Ltd. (N/A)
|
Family
ID: |
40129383 |
Appl.
No.: |
12/601,992 |
Filed: |
May 7, 2008 |
PCT
Filed: |
May 07, 2008 |
PCT No.: |
PCT/JP2008/001149 |
371(c)(1),(2),(4) Date: |
November 25, 2009 |
PCT
Pub. No.: |
WO2008/152768 |
PCT
Pub. Date: |
December 18, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100197506 A1 |
Aug 5, 2010 |
|
Foreign Application Priority Data
|
|
|
|
|
Jun 12, 2007 [JP] |
|
|
2007-155484 |
|
Current U.S.
Class: |
505/238;
505/237 |
Current CPC
Class: |
H01L
39/2461 (20130101) |
Current International
Class: |
H01L
39/24 (20060101) |
Field of
Search: |
;505/237,238 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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04-329867 |
|
Nov 1992 |
|
JP |
|
04-331795 |
|
Nov 1992 |
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JP |
|
2005-113220 |
|
Apr 2005 |
|
JP |
|
2007-115561 |
|
May 2007 |
|
JP |
|
Primary Examiner: Wartalowicz; Paul
Attorney, Agent or Firm: Bacon & Thomas, PLLC
Claims
The invention claimed is:
1. A tape-shaped oxide superconductor having an intermediate layer
and an oxide superconducting layer provided in series onto a
biaxially-oriented metallic substrate, comprising: a three-layer
structured intermediate layer including a first intermediate layer
which is formed onto said metallic substrate and comprises an oxide
which has a template function, a second intermediate layer which is
formed onto said first intermediate layer and comprises an oxide
which has a function which prevents diffusion to said oxide
superconducting layer of an element which composes said metallic
substrate, and a third intermediate layer which is formed onto said
second intermediate layer and comprises an oxide which has a
function which controls an orientation of said oxide
superconducting layer; and wherein the first intermediate layer is
Ce--RE.sub.1--O, wherein RE.sub.1 is at least one element selected
from the group consisting of Gd, Sm, Eu, Dy, Ho, and Er, and
wherein a mole ratio of Ce:RE.sub.1 of the first intermediate layer
is within the range of Ce:RE.sub.1=40:60-70:30 and the third
intermediate layer is CeO.sub.2.
2. A tape-shaped oxide superconductor according to claim 1, wherein
in-plane orientations from the first intermediate layer to the
third intermediate layer are within the range of .+-.1.0 degree for
.DELTA..phi. (half value width) by X-ray diffraction of the
biaxially-oriented metallic substrate.
3. A tape-shaped oxide superconductor according to claim 1, wherein
the first intermediate layer has a thickness within the range of
10-100 nm.
4. A tape-shaped oxide superconductor according to claim 1, wherein
the third intermediate layer has a thickness of 30 nm or more.
5. A tape-shaped oxide superconductor according to claim 1, wherein
the oxide superconducting layer has a structure of
RE.sub.3Ba.sub.2Cu.sub.3O.sub.7-y, wherein RE.sub.3 is at least one
element selected from the group consisting of Y, Gd, Sm, Nd, Ho,
Dy, Eu, Tb, Er, and Yb.
6. A tape-shaped oxide superconductor according to claim 1, wherein
the second intermediate layer is formed by RE.sub.2--Zr--O, wherein
RE.sub.2 is at least one element selected from the group consisting
of Ce, Gd, Sm, Eu, Dy, Ho, Er, and Y.
7. A tape-shaped oxide superconductor according to claim 6, wherein
a mole ratio of RE.sub.2:Zr of the second intermediate layer is
within the range of RE.sub.2:Zr=30:70-70:30.
8. A tape-shaped oxide superconductor according to claim 7, wherein
the second intermediate layer has a thickness within the range of
30 nm or more.
9. A tape-shaped oxide superconductor according to claim 1, wherein
the first and the second intermediate layers and the oxide
superconducting layer are formed by an organic metallic salt
coating thermal decomposition (MOD).
10. A tape-shaped oxide superconductor according to claim 9,
wherein the first and the second intermediate layers and the oxide
superconducting layer are formed by giving a heat-treatment after
coating a mixed solution of an octylic acid salt, a naphthenate, a
neodecanoic acid salt, or a trifluoroacetate which includes an
element which composes the intermediate layer or the oxide
superconducting layer.
11. A tape-shaped oxide superconductor according to claim 1,
wherein the biaxially-oriented metallic substrate is provided with
a biaxially-oriented surface layer on a side which contacts at
least the first intermediate layer.
12. A tape-shaped oxide superconductor according to claim 11,
wherein the biaxially-oriented metallic substrate is provided with
a biaxially-oriented surface layer on a side which contacts at
least the first intermediate layer by giving a heat-treatment after
a cold rolling of Ni, Ni-base alloy, Cu, or Cu-base alloy.
13. A tape-shaped oxide superconductor according to claim 12,
wherein the biaxially-oriented metallic substrate comprises the
Ni-base alloy which includes Ni and 0.1-15 at % of at least one
element selected from the group consisting of W, Mo, Ta, V, and
Cr.
14. A tape-shaped oxide superconductor, comprising: a three-layer
structured intermediate layer including a first intermediate layer,
a second intermediate layer, and a third intermediate layer formed
in series on a surface layer of Ni-base alloy which includes Ni and
at least one element selected from the group consisting of W, Mo,
Ta, V, and Cr and which is provided with a biaxially-oriented
surface layer at least at a face of one side, said first
intermediate layer being Ce--Gd--O which is formed by an organic
metallic salt coating thermal decomposition (MOD) and wherein a
mole ratio of Ce:Gd is within the range of 40:60-70:30, said first
intermediate layer having a thickness of 10-100 nm, said second
intermediate layer being Ce--Zr--which is formed by the organic
metallic salt coating thermal decomposition (MOD), said second
intermediate layer having a thickness of 30 nm or more and a mole
ratio Ce:Zr within the range of 30:70-70:30, said third
intermediate layer being CeO.sub.2 and having a thickness of 30 nm
or more, wherein the first intermediate layer to the third
intermediate layer have in-plane orientations within the range of
.+-.1.0 degree for .DELTA..phi. (half value width) by a X-ray
diffraction of a biaxially-oriented metallic substrate, and wherein
an YBa.sub.2Cu.sub.3O.sub.7-y superconducting layer, formed by
organic metallic salt coating thermal decomposition (MOD), is
superimposed on the three-layered structured intermediate layer.
Description
TECHNICAL FIELD
This invention relates to an oxide superconductor which is suitable
to the usage for an electric power cable, an electric power device
such as an electric power storage system, and a power application
product such as a motor and a transformer. In particular, this
invention relates to a tape-shaped oxide superconductor which is
suitable to a film formation method, that is, an organic metallic
salt coating thermal decomposition (MD) method that a ceramics thin
layer is formed onto a metallic substrate by heating and baking a
precursor film.
BACKGROUND ART
As for the oxide superconductor, a critical temperature (Tc) is
high compared with a conventional metal system, superconductor such
as Nb.sub.3Sn system, and the electric power cable, and applied
equipments such as transformer, motor, and electric power storage
system can be operated under the liquid nitrogen temperature.
Therefore, the making of the wire rod is studied energetically.
Especially, in RE.sub.3Ba.sub.2Cu.sub.3O.sub.7-y (here, RE.sub.3
shows any one kind or more than two kinds of elements selected from
Y, Gd, Sm, Nd, Ho, Dy, Eu, Tb, Er, Yb, and hereinafter called
RE.sub.3BCO) superconductor, because the attenuation of the
conducting current is small in the high magnetic field area, that
is, because the magnetic-field property in the liquid nitrogen
temperature is excellent compared with Bi system superconductor,
the practical high critical current density (Jc) can be maintained.
And, in addition to the excellent property in the high temperature
area, because the manufacturing method which does not use silver of
the precious metal is possible and the liquid nitrogen can be used
as the refrigerant, the cooling efficiency improves remarkably.
Therefore, it is extremely advantageous economically and the making
of the wire rod is expected as the next-generation superconducting
material.
Generally, the RE.sub.3BCO oxide superconducting wire rod has the
structure that at least one layer or a plurality of layers of the
biaxially-oriented oxide layer are formed onto the metallic
substrate, and the oxide superconducting layer is formed onto it,
and further, the stabilizing layer which undertakes the role as the
surface protection of the superconducting layer, the improvement of
the electric contact, and the protection circuit at the time of the
excessive energization is stacked. In this case, it is known that
the critical current property of the RE.sub.3BCO wire rod depends
on the in-plane orientation of the superconducting layer, and is
influenced greatly by the intermediate layer which becomes the
basic material and by the in-plane orientation and the smooth
surface property of the oriented metallic substrate.
The crystal system of the RE.sub.3BCO oxide superconductor is the
rhombic crystal, and because the lengths of three sides of x axis,
y axis and z axis are different and the angles among the three
sides of the unit cell are also slightly different respectively, it
is easy to form the twin crystal. And because the slight gap of the
azimuth generates the twin crystal grain boundary and reduces the
conducting property, to bring out the property of the material in
the conducting state, in addition to alignment of the CuO face of
the inside of the crystal, the alignment of the crystal orientation
in the in-plane also is demanded. Therefore, the making of the wire
rod has the difficulty compared with the Bi system oxide
superconductor.
The manufacturing method of the making of the wire rod which
improves the in-plane orientation of the crystal of the RE.sub.3BCO
oxide superconductor and aligns the azimuth direction in the
in-plane is same as the manufacturing method of the thin film. That
is, the intermediate layer whose in-plane orientation and azimuth
direction are improved is formed onto the tape-shaped metallic
substrate, and the crystal lattice of this intermediate layer is
used as the template. And thereby, the in-plane orientation and the
azimuth direction of the crystal of the Re.sub.3BCO oxide
superconducting layer are improved.
The RE.sub.3BCO oxide superconductor is studied in various
manufacturing processes now, and various biaxially-oriented
composite substrates which form the in-plane oriented intermediate
layer onto the tape-shaped metallic substrate are known.
Among these, at present, the process which shows the highest
critical current property is a method of using the IBAD (Ion Beam
Assisted Deposition) substrate. In this method, onto the
polycrystalline non-magnetic and high strength tape-shaped Ni
system substrate (hastelloy etc.), the particle generated from the
target while irradiating the ion from a direction of the constant
angle for the normal line of this Ni system substrate is deposited
by pulsed laser deposition (PLD) method. And, the intermediate
layer (CeO.sub.2, Y.sub.2O.sub.3, YSZ etc.) or the intermediate
layer of the double-layered structure (YSZ or
RxZr.sub.2O.sub.7/CeO.sub.2 or Y.sub.2O.sub.3 etc.: Rx shows Y, Nd,
Sm, Gd, Eu, Yb, Ho, Tm, Dy, Ce, La or Er) which has the fine grain
size and the high orientation and inhibits the reaction with the
element which composes the superconductor is formed. And, after
forming the CeO.sub.2 film onto it by PLD method, in addition,
YBa.sub.2Cu.sub.3O.sub.7-y (hereinafter called YBCO) layer is
formed by PLD method or CVD method, and the superconducting wire
rod is formed (for example, refer to Patent document No. 1 to No.
3).
However, in this process, because all intermediate layers are
formed by the vacuum process in the gas phase method, although this
process has the advantage that the dense and smooth intermediate
layer film can be obtained, there are problems that the production
speed is slow and the production cost rises. Although the processes
of forming films by using some gas phase methods other than this
IBAD method have been studied, the effective means which solve the
problems of the production speed and the production cost have not
been reported.
The most effective process for attaining the low cost is the MOD
process where the organic acid salt or the organic metallic
compound is used as the raw material and the oxide layer is formed
by giving the thermal decomposition and the crystallization
heat-treatment after coating this solution onto the surface of the
substrate. Although this process is simple, because the long time
heat-treatment in high temperature is necessary, by the generation
of cracks due to the contraction in volume of film at the time of
the thermal decomposition, the non-uniform reaction by the
imperfect of grain growth, and the decrease of the crystalline by
such as the diffusion through the crystal grain boundary of the
metallic element which composes the substrate, it was difficult to
obtain the film having the function enough as the intermediate
layer.
Generally, as the intermediate layer of the superconductor,
especially in the case of YBCO, although CeO.sub.2 which is formed
by PVD method is used as described above, because CeO.sub.2
intermediate layer is excellent in the lattice consistency with the
YBCO layer and in the oxidation resistance, and because the
reactive property with the YBCO layer is small, this depends on
what is known as one of the most excellent intermediate layer. When
this CeO.sub.2 intermediate layer is formed by MOD method, the
cracks are generated due to the large difference of the coefficient
of thermal expansion with the metal of the substrate, and it
becomes impossible to accomplish the function as the intermediate
layer. When the film is formed by MOD method onto the Ni substrate
by the solid solution that Gd is added to CeO.sub.2, although the
generation of cracks is inhibited by being able to alleviate the
difference of the coefficient of thermal expansion, because the
diffusion of the element from Ni or Ni alloy substrate cannot be
stopped in the inside of the intermediate layer, there was a
problem that the superconducting property decreases.
In order to prevent the diffusion of the element which composes
this substrate, the study of the intermediate layer material
(Ce.sub.2Zr.sub.2O.sub.7) that a part of CeO.sub.2 is substituted
to Zr is carried out. And for example, in the oxide superconductor
that one layer or a plurality of layers of the biaxially-oriented
intermediate layer by the inorganic material is formed and the
oxide superconducting layer is provided onto this, by providing the
intermediate layer which includes one kind of element selected from
Ce, Gd or Sm and Zr onto the above-mentioned substrate, the effect
of preventing the diffusion to the superconducting layer of the
metallic element which composes the substrate is admitted, and the
property of Jc>1MA/cm.sup.2 is obtained (refer to Patent
application No. 2005-306696 and Patent application No.
2005-360788). Patent document No. 1: Japanese Patent Publication
No. Hei04-329867 Patent document No. 2: Japanese Patent Publication
No. Hei04-331795 Patent document No. 3: Japanese Patent Publication
No. 2002-203439
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
As described above, when the intermediate layer is formed by the
material (Ce.sub.2Zr.sub.2O.sub.7) that a part of CeO.sub.2 is
substituted to Zr, the effect of preventing the diffusion to the
superconducting layer of the element which composes the metallic
substrate is admitted. However, if the oxide layer which includes
Zr is provided directly onto the metallic substrate, the
orientation deteriorates 1-3 degrees than the metallic substrate.
Therefore, because the orientation of the superconducting layer
also deteriorates depending on this, there was a problem that the
improvement of the superconducting property cannot expect. That is,
in this system, it is difficult to equalize the in-plane
orientations of the intermediate layer and the oxide
superconducting layer which are important factor for improving Jc
for the substrate, and thereby, there was a conclusion that the
improvement of Jc of the superconducting layer was disturbed.
This invention was conducted to solve the above-described problems.
And this invention as to provide the tape-shaped oxide
superconductor which is excellent in the superconducting property
by preventing the diffusion to the superconducting layer of the
element which composes the metallic substrate, by preventing the
generation of the cracks due to the difference of the coefficient
of thermal expansion with the metal of the substrate, and by
improving the orientation of the superconducting layer.
Means for Solving the Problems
The tape-shaped oxide superconductor of this invention was
conducted to solve the above-described problems. In a tape-shaped
oxide superconductor that an intermediate layer and a oxide
superconducting layer are formed in series onto a
biaxially-oriented metallic substrate, the intermediate layer is
formed by three-layer structure which comprises a first
intermediate layer which is formed onto the metallic substrate and
comprises an oxide which has a template function, a second
intermediate layer which is formed onto the first intermediate
layer and comprises an oxide which has a function which prevents a
diffusion to the oxide superconducting layer of an element which
composes the metallic substrate, and a third intermediate layer
which is formed onto the second intermediate layer and comprises an
oxide which has a function which controls an orientation of the
oxide superconducting layer.
In the above-described case, in order to succeed an in-plane
orientation of a crystalline of a surface of the biaxially-oriented
metallic substrate and improve the in-plane orientation of the
oxide superconducting layer, it is preferable that the in-plane
orientation from the first intermediate layer to the third
intermediate layer are maintained within the range of .+-.1.0
degree for .DELTA..phi. (FWHM: half value width) of the
biaxially-oriented metallic substrate.
It is possible that the above-mentioned first intermediate layer
and third intermediate layer are formed by CeO.sub.2 or
Ce--RE.sub.1--O (here, RE.sub.1 shows any one kind or more than two
kinds of elements selected from Gd, Sm, Eu, Dy, Ho, Er, and
hereinafter it is same.).
Besides, it is possible that the second intermediate layer is
formed by RE.sub.2--Zr--O (here, RE.sub.2 shows any one kind or
more than two kinds of elements selected frau Ce, Gd, Sm, Eu, Dy,
Ho, Er, Y, and hereinafter it is same.)
It is preferable that the first and the second intermediate layers
and the oxide superconducting layer are formed by an organic
metallic salt coating thermal decomposition (MOD) method.
In this case, it is possible that these intermediate layer and
oxide superconducting layer are formed by giving a heat-treatment
after coating a mixed solution of an octylic acid salt, a
naphthenate, a neodecanoic acid salt, or a trifluoroacetate which
includes each element which composes the aforementioned
intermediate layer or oxide superconducting layer with a predefined
mole ratio.
Besides, in this invention, although the biaxially-oriented
metallic substrate is used, it is necessary that this metallic
substrate is provided with a biaxially-oriented surface layer in a
side which contacts to at least the first intermediate layer. And,
it is possible that the metallic substrate like this are obtained
by giving a predefined heat-treatment after a cold rolling of Ni,
Ni-base alloy, Cu, or Cu-base alloy.
Effect of the Invention
According to this invention, by providing the three-layer
structured intermediate layers which have the particular functions
respectively onto the biaxially-oriented metallic substrate, the
first intermediate layer succeeds the in-plane orientation of the
metallic substrate as the template of the metallic substrate, and
the diffusion to the oxide superconducting layer of the element
which composes the metallic substrate is prevented by the second
intermediate layer which is stacked onto that, and further, the
third intermediate layer controls the orientation of the oxide
superconducting layer which is stacked onto that. Therefore, the
diffusion of the element which composes the metallic substrate or
the generation of the cracks in the intermediate layer can be
prevented. Besides, it is possible that the in-plane orientation of
the oxide superconducting layer is equally maintained with the
metallic substrate, and the tape-shaped oxide superconductor which
is excellent in the superconducting property can be obtained.
BRIEF DESCRIPTION OF THE FIGURES
[FIG. 1] The schematic sectional view which is perpendicular to the
axial direction of the tape which shows one embodiment of the
tape-shaped oxide superconductor of this invention.
[FIG. 2] The schematic sectional view which is perpendicular to the
axial direction of the tape which shows other embodiment of the
tape-shaped oxide superconductor of this invention.
[FIG. 3] The schematic sectional view which is perpendicular to the
axial direction of the tape which shows one embodiment of the
structure of the tape-shaped oxide superconductor of this
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 3, the tape-shaped oxide superconductor of this
invention has the structure that the first intermediate layer
(template layer) 11 which has the equivalent orientation with the
metallic substrate over the oriented metallic substrate 10 which
has the biaxially-orientation, the second intermediate layer
(diffusion preventing layer) 12 which prevents the diffusion of the
metallic element which composes the oriented metallic substrate 10
to the oxide superconducting layer, and the third intermediate
layer (orientation controlling layer) 13 which controls the
orientation of the oxide superconducting layer and prevents the
reactivity are stacked, since then, the superconducting layer 14 is
provided onto this. Further, the stabilizing layer (not shown in
drawing) which has the role of such as surface protection
comprising such as silver may be provided onto the oxide
superconducting layer 14.
As for above-mentioned each intermediate layer 11, 12, 13, it is
necessary to succeed the orientation of the crystalline of the
biaxially-oriented oriented metallic substrate 10 for improving the
in-plane orientation of the oxide superconducting layer 14.
Therefore, as for the metallic substrate 10, it is necessary to
provide the biaxially-oriented surface layer in the side which
contacts to at least first intermediate layer. As the oriented
metallic substrate like this, Ni, Ni-base alloy, Cu or Cu-base
alloy that the predefined heat-treatment is given after cold
rolling can be used. For example, Ni-base alloy which includes any
one kind or more than two kinds of elements selected from (W, Mo,
Ta, V, Cr) into Ni with 0.1-15 at % can be used. Besides, the
composite metallic substrate which comprises the stacking structure
that these oriented metallic substrate, the metallic substrate
(hastelloy, inconel, stainless steel, etc.) which has the heat
resistance and the oxidation resistance, and Ni, Ni-base alloy, Cu,
or Cu base-alloy are attached together by the cold rolling and the
heat-treatment for the orientation is given with the temperature of
90-1300 degrees C. can be also used. Instead of the oriented
metallic substrate 1 which has the biaxially-orientation of FIG. 3,
FIG. 2 shows the example of using the composite metallic substrate
that the metallic substrate 10b which has the heat resistance and
the oxidation resistance and the oriented metallic substrate 10a
which has the biaxially-orientation are attached together.
It is preferable that the first intermediate layer 11 and the third
intermediate layer 13 are formed by CeO.sub.2 or Ce--RE.sub.1--O.
In this case, the mole ratio of Ce:RE.sub.1 is within the range of
Ce:RE.sub.1=30:70-(100-.alpha.):.alpha.(.alpha.>0). And more
preferably, it is within the range of Ce:RE.sub.1=40:60-70:30. This
reason is that the biaxially-orientation decreases when Ce/RE.sub.1
ratio is smaller than 3/7.
It is preferable that the thickness of the first intermediate layer
11 is within the range of 10-100 nm. This reason is that when the
film thickness is less than 10 nm, the metallic substrate cannot be
coated perfectly and the effect of improving the orientation is not
admitted, and on the other hand, when the film thickness exceeds
100 nm, the surface roughness increases, and the orientations of
the second intermediate layer and the third intermediate layer and
the superconducting property of the superconducting layer decrease
remarkably.
Besides, it is preferable that the thickness of the third
intermediate layer 13 is the range of 30 nm or more. When the film
thickness is less than 30 nm, at the time of film formation of the
superconducting layer, the superconducting layer and the third
intermediate layer 13 react and disappears, therefore, the
superconducting property decreases remarkably.
On the other hand, the second intermediate layer 12 can be formed
by RE.sub.2--Zr--O. In this case, it is preferable that the mole
ratio of RE.sub.2:Zr is within the range of
RE.sub.2:Zr=30:70-70:30. It is preferable that the thickness of the
second intermediate layer 12 is the range of 30 nm or more. When
the film thickness is less than 30 nm, at the time of the film
formation of the superconducting layer, because the interdiffusion
between the alloy element which composes the metallic substrate 10
and the superconducting layer occurs, the superconducting property
deteriorates remarkably.
As for the above-mentioned first to third intermediate layers and
the oxide superconducting layer, it is possible to use any method
such as the organic metallic salt coating thermal decomposition
(MOD) method, the RF sputtering method, the pulsed laser deposition
method, the EB method, and the CVD method if the above-mentioned
oxide can be formed. However, from the above-mentioned reason, it
is preferable to form the first and second intermediate layers and
the oxide superconducting layer by the organic metallic salt
coating thermal decomposition (MOD) method. In this case, these
intermediate layer and oxide superconducting layer can be formed by
giving the heat treatment after coating the mixed solution of the
octylic acid salt, the naphthenate, the neodecanoic acid salt, or
the trifluoroacetate which include the element which composes the
aforementioned intermediate layer and oxide superconducting layer
with predefined mole ratio. And if these can be dissolved uniformly
into one kind or more than two kinds of organic solvent and coated
onto substrate, it is not limited by this example.
In this case, TFA-MOD method is preferable for the formation of the
oxide superconducting layer. This method is known as the method of
producing by the non-vacuum process. The solution of the metal
organic acid salt including the trifluoroacetate (TFA salt) which
includes each metallic element which composes the oxide
superconductor with predefined mole ratio is coated onto the
substrate, and the amorphous precursor is formed by giving the
preliminary calcination heat-treatment to it, and then, the
crystallization heat-treatment is given, and the oxide
superconductor is formed by crystallizing the precursor.
As for the coating method to the metallic substrate, such spin coat
method, dip coat method, or ink-jet method are enumerated. However,
if the uniform film to the substrate can be formed, it is not
limited by this example.
Although the in-plane orientation of the first intermediate layer
11 by MOD method is formed in the range of about -2 degrees-+5
degrees for .DELTA..phi. (half value width) by the X-ray
diffraction of the oriented metallic substrate 10 which has the
biaxially-orientation, preferably, the in-plane orientations from
the first intermediate layer to the third intermediate layer are
maintained within the range of .+-.1.0 degree for .DELTA..phi.
(half value width) of the oriented metallic substrate 10 which has
the biaxially-orientation.
It is preferable that the oxide superconducting layer which is
formed onto the third intermediate layer has the structure of
RE.sub.3Ba.sub.2Cu.sub.3O.sub.7-y (here, RE.sub.3 shows any one
kind or more than two kinds of elements selected from Y, Gd, Sm,
Nd, Ho, Dy, Eu, Tb, Er, or Yb). Particularly, it is preferable that
it is formed by an YBa.sub.2Cu.sub.3O.sub.7-y (hereinafter called,
YBCO) superconductor.
From the above, as more preferable embodiment of the tape-shaped
oxide superconductor of this invention, onto the surface layer of
the Ni-base alloy which includes any one kind or more than two
kinds of elements selected from (W, Mo, Ta, V, Cr) into Ni, and
which is provided with the biaxially-oriented surface layer at the
face of at least one side, the three-layer structured intermediate
layer that the first intermediate layer, the second intermediate
layer, and the third intermediate layer are formed in series is
provided. The first intermediate layer is formed by CeO.sub.2 which
is formed by the organic metallic salt coating thermal
decomposition (MOD) method whose thickness is 10-100 nm or by
Ce--Gd--O oxide whose mole ratio is within the range of
Ce:Gd=40:60-70:30, the second intermediate layer is formed by
Ce--Er--O oxide which is formed by the organic metallic salt
coating thermal decomposition (MOD) method whose thickness is 30 nm
or more and whose mole ratio is within the range of
Ce:Gd=30:70-70:30, and the third intermediate layer is formed by
CeO.sub.2 whose thickness is 30 nm or more or by Ce--Gd--O oxide
whose mole ratio is within the range of Ce:Gd=40:60-70:30. And the
in-plane orientation from the first intermediate layer to the third
intermediate layer can be maintained within the range of .+-.1.0
degree for .DELTA..phi. (half value width) by the X-ray diffraction
of the biaxially-oriented metallic substrate, and YBCO oxide
superconductor can be formed by the organic metallic salt coating
thermal decomposition (MOD) method onto this intermediate
layer.
Embodiment
Hereinafter, the embodiments of this invention and the comparative
examples are explained.
EXAMPLE 1-8
As shown in FIG. 1, onto the Ni-base alloy substrate of the width
of 5 mm and the thickness of 70 .mu.m, Ce--Gd--O system oxide layer
2 as the first intermediate layer and Ce--Zr--O system oxide layer
3 as the second intermediate layer were formed by MOD method. As
the result of measurement by X-ray diffraction, the orientation of
the crystalline of the Ni-base alloy substrate 1 was 6.5 degrees in
the .DELTA..phi. (half value width).
Ce--Gd--O system oxide layer 2 was formed by carrying out the
preliminary calcination in the range of 100-400 degrees C. after
coating the mixed solution of the organic metallic salt such as the
octylic acid, the naphthenic acid or the neodecanoic acid which
includes Ce and Gd with predefined mole ratio respectively by using
the Dip coating, and then by crystallizing the film by giving the
baking in the range of 900-1200 degrees C.
Besides, Ce--Zr--O system oxide layer 3 was formed as the film onto
Ce--Gd--O system oxide layer 2 by using the mixed solution of the
organic metallic salt such as the octylic acid, the naphthenic acid
or the neodecanoic acid which includes Ce and Zr with the mole
ratio of Ce:Zr=50:50, and by the method similar to the
above-mentioned. The film thickness at this time was 100 nm.
Onto the above-mentioned Ce--Zr--O system oxide layer 3, by RF
sputtering method, the film of CeO.sub.2 oxide layer 4 of the film
thickness of 150 nm was formed as the third intermediate layer by
using the CeO.sub.2 target and by controlling the Ni-base alloy
substrate 1 with the range of the temperature of 400-750 degrees
C.
Onto the three-layer structured intermediate layer which was formed
by the above-mentioned, the film of YBCO superconducting layer 5
was formed by TFA-MOD method. As for the condition of the film
formation at this time, after coating the mixed raw material
solution of the metal organic acid salt which includes the
trifluoroacetate (TFA salt) onto CeO.sub.2 oxide layer 4, the film
was formed with the range of the temperature of 710-780 degrees C.
by carrying out the normal calcination of the preliminary
calcination film which was formed by the preliminary calcination.
The range of the whole pressure at the time of the calcination was
5-800 Torr., the oxygen partial pressure was 100-5000 ppm, and the
water vapor partial pressure was 2-30%. The film thickness of YBCO
superconducting layer 5 which was formed in this way was 1
.mu.m.
As for the Jc of the tape-shaped oxide superconductor which was
formed by the above-mentioned in the liquid nitrogen, the
composition, the film thickness, and the .DELTA..phi. of the
Ce--Gd--O system oxide layer 2 which is the first intermediate
layer, the .DELTA..phi. of the Ce--Zr--O system oxide layer 3 which
is the second intermediate layer, and the .DELTA..phi. of the
CeO.sub.2 oxide layer 4 which is the third intermediate layer were
shown together in the table 1.
TABLE-US-00001 TABLE 1 First intermediate layer .DELTA. .phi. (Half
value width: degree) Film First Second Third Jc of Ce:Gd thickness
intermediate intermediate intermediate YBCO film Example (Mole
ratio) (nm) layer layer layer (MA/cm.sup.2) 1 50:50 15 6.0 6.1 6.0
2.1 2 50:50 50 6.2 6.0 6.0 2.2 3 50:50 75 6.2 6.3 6.2 2.1 4 50:50
100 6.4 6.2 6.2 2.1 5 60:40 50 6.5 6.6 6.6 1.8 6 70:30 50 6.5 6.4
6.3 2.0 7 90:10 50 6.4 6.4 6.4 1.9 8 40:60 50 6.3 6.4 6.3 1.8 Note)
First intermediate layer: Ce--Gd--O system oxide layer Second
intermediate layer: Ce--Zr--O system oxide layer Third intermediate
layer: CeO.sub.2 oxide layer
EXAMPLE 9-12
The tape-shaped oxide superconductor was formed by the method
similar to Embodiment 1-8 except that the CeO.sub.2 oxide layer
(Embodiment 9), Ce--Sm--O oxide layer (Embodiment 10), Ce--Eu--O
oxide layer (Embodiment 11), and Ce--Ho--O oxide layer (Embodiment
12) as the first intermediate layer was formed.
As for the Jc of the tape-shaped oxide superconductor which was
formed in this way in the liquid nitrogen, the composition, the
film thickness, and the .DELTA..phi. of the first intermediate
layer, the .DELTA..phi. of the Ce--Zr--O system oxide layer 3 which
is the second intermediate layer, and the .DELTA..phi. of the
CeO.sub.2 oxide layer 4 which is the third intermediate layer were
shown together in the table 2.
TABLE-US-00002 TABLE 2 First intermediate layer .DELTA. .phi. (Half
value width: degree) Film First Second Third Jc of Ce:Re.sub.1
thickness intermediate intermediate intermediate YBCO film Example
Oxide (Mole ratio) (nm) layer layer layer (MA/cm.sup.2) 9 CeO.sub.2
100:0 50 6.5 6.5 6.4 1.7 10 Ce--Sm--O 50:50 50 6.7 6.6 6.7 1.7 11
Ce--Eu--O 50:50 50 6.7 6.8 6.7 1.6 12 Ce--Ho--O 50:50 50 6.8 7.0
7.0 1.6 Note) Second intermediate layer: Ce--Zr--O system oxide
layer Third intermediate layer: CeO.sub.2 oxide layer
COMPARATIVE EXAMPLE 1-4
As the first intermediate layer, Ce--Gd--O system oxide layer
(Comparative example 1 to 3) whose composition and film thickness
were changed was formed, and further, the tape-shaped oxide
superconductor was formed by the method similar to Embodiment 1-8
except the case (Comparative example 4) that the first intermediate
layer was not formed onto the Ni-base alloy substrate 1.
As the Jc of the tape-shaped oxide superconductor which was formed
in this way in the liquid nitrogen, the composition, the film
thickness, and the .DELTA..phi. of the first intermediate layer,
the .DELTA..phi. of the Ce--Zr--O system oxide layer 3 which is the
second intermediate layer, and the .DELTA..phi. of the CeO.sub.2
oxide layer 4 which is the third intermediate layer were shown
together in the table 3.
TABLE-US-00003 TABLE 3 First intermediate layer .DELTA. .phi. (Half
value width: degree) Film First Second Third Jc of Comparative
Ce:Re.sub.1 thickness intermediate intermediate intermediate - YBCO
film example Oxide (Mole ratio) (nm) layer layer layer
(MA/cm.sup.2) 1 Ce--Gd--O 50:50 5 Measurement 9.0 9.0 0.7 is not
possible 2 Ce--Gd--O 50:50 120 7.0 8.5 8.5 0.8 3 Ce--Gd--O 20:80 50
10.0 10.0 10.0 0.6 4 None -- -- -- 8.5 8.5 1.0 Note) Second
intermediate layer: Ce--Zr--O system oxide layer Third Intermediate
layer: CeO.sub.2 oxide layer
Industrial Applicability
In the tape-shaped oxide superconductor according to this
invention, the utilization to the oxide superconductor which is
suitable to the usages to the electric power cable, the electric
power equipment such as the electric power storage system and the
power equipment such as the motor is possible.
* * * * *